1. Field of Invention
Various embodiments of the present disclosure relate to a clock synchronization method and apparatus and, more particularly, to a method and apparatus for performing clock synchronization by determining a clock offset and a network delay between a master and a slave in an IEEE 1588 system.
2. Description of Related Art
In IEEE 1588 systems, as technology for synchronizing the clocks of nodes, an IEEE 1588 Precision Time Protocol (PTP) is used. The IEEE 1588 PTP estimates clock offset between nodes based on the packet delay estimation to synchronize clocks between nodes. For example, in a network with the IEEE 1588 PTP, all slave nodes synchronize their clocks with that of a master node by estimating clock offset between the slave node and the master node based on the packet delay estimation.
The clock offset estimation based on the packet delay estimation of the IEEE 1588 PTP is frequently used in various network systems owing to the simple structure and high performance thereof. However, in actual network systems, the IEEE 1588 PTP has a tendency to deteriorate the performance thereof due to various factors. As the factors deteriorating the performance of the IEEE 1588 PTP, there are various factors, such as an asymmetry of the packet delay, a clock skew, an algorithm for selecting the master node and a failure in synchronization with the master.
However, the most significant factor that deteriorates performance in the IEEE 1588 PTP is the inaccuracy of estimation of the packet delay due to the asymmetry of the packet delay. More specifically, in the IEEE 1588 PTP, the packet delay from the master to the slave and the packet delay from the slave to the master are assumed to be identical to each other. However, in an actual network environment, the two packet delays are not identical to each other due to various environmental variables, such as jitter. Therefore, such inaccurate estimation causes errors in estimating the clock offset between the master and the slave, and makes it impossible to completely synchronize the clocks of the master and the slave with each other.